Gives us the lowest HW sample rate that's >= 22KHz.
Needed because some targets that don't support 22K support 11K or 8K, so
HW_SAMPR_MIN will give us much lower quality than is acceptable.
Take advantage of this new macro in the SDL, MIDI, and MIKMOD plugins,
and implement a crude "fast enough" test to enable higher sample rates
on more capable targets.
Change-Id: I6ad38026fb3410c62da028e78512e027729bb851
